Java 试图设置index.jsp的NullPointerException

EDIT:我通过将

index.jsp

重命名为

hi.jsp

解决了这个问题。有人知道为什么我的文件名有问题吗

问题： 我使用Java/Spring编写了webapp的后端组件，并通过Spring注释将其连接到Tomcat：

@Controller
public class WorkerSubmitterController {
    @RequestMapping(value = {"/start"}, method = RequestMethod.GET, produces = "text/plain")
    @ResponseBody
    public ResponseEntity<String> start() throws Exception {
        return new ResponseEntity<String>("Started", HttpStatus.OK);
    }
}

我添加了一个

web.xml

文件：

<web-app id="WebApp_ID" version="2.4"
         xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
    http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">

    <servlet>
        <servlet-name>home</servlet-name>
        <jsp-file>/index.jsp</jsp-file>
    </servlet>
    <servlet-mapping>
        <servlet-name>home</servlet-name>
        <url-pattern>/home</url-pattern>
    </servlet-mapping>

</web-app>

服务器端显示：

2013-10-08 20:27:31.652:WARN:oejs.ServletHandler:/home
java.lang.NullPointerException
    at java.net.URLEncoder.encode(URLEncoder.java:205)
    at java.net.URLEncoder.encode(URLEncoder.java:171)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:474)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:378)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:848)
    at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:669)
    at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:457)
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:137)
    at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:557)
    at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:231)
    at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1075)
    at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:384)
    at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:193)
    at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1009)
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:135)
    at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:255)
    at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:154)
    at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:116)
    at org.eclipse.jetty.server.Server.handle(Server.java:368)
    at org.eclipse.jetty.server.AbstractHttpConnection.handleRequest(AbstractHttpConnection.java:489)
    at org.eclipse.jetty.server.AbstractHttpConnection.headerComplete(AbstractHttpConnection.java:942)
    at org.eclipse.jetty.server.AbstractHttpConnection$RequestHandler.headerComplete(AbstractHttpConnection.java:1004)
    at org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:640)
    at org.eclipse.jetty.http.HttpParser.parseAvailable(HttpParser.java:235)
    at org.eclipse.jetty.server.AsyncHttpConnection.handle(AsyncHttpConnection.java:82)
    at org.eclipse.jetty.io.nio.SelectChannelEndPoint.handle(SelectChannelEndPoint.java:628)
    at org.eclipse.jetty.io.nio.SelectChannelEndPoint$1.run(SelectChannelEndPoint.java:52)
    at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:608)
    at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:543)
    at java.lang.Thread.run(Thread.java:724)

我做错了什么？我是否错过了使.jsp页面正常工作的步骤？

index.jsp

不正确吗？我试着将

index.jsp

修改为

hello

，同样的错误会弹出。此外，我还尝试移动

index.jsp

文件来查找问题的根源，错误消失了，但是我得到了

Oct 08, 2013 9:58:38 PM org.apache.jasper.servlet.JspServlet serviceJspFile
SEVERE: PWC6117: File "%2FUsers%2FuserName%2Fpersonal%2Friver%2Fsrc%2Fmain%2Fwebapp%2FWEB-INF%2Findex.jsp" not found 

---

因此，我猜问题与我的JSP文件有关。

问题是您试图访问

WEB-INF

目录中的JSP，该目录显然无法访问。您试图从根目录访问它，这就是为什么会出现错误

httperror404

然而，现在我正试图通过让index.jsp工作来编写前端。我在/webapp/WEB-INF/下创建了一个index.jsp文件，其中包含以下内容：…

---

尝试将JSP从

WEB-INF

文件夹移动到应用程序的根目录中。

这似乎是一个警告，而不是错误。您没有声明文件的编码吗？我以前在index.jsp的顶部有，但它仍然给我相同的错误，我还尝试添加了是的，就是这样！Thanks@Popcorn作为补充信息。故意将JSP文件放在WEB-INF中以防止客户端brouser直接访问也是一种广泛的安全实践（当然，如果您需要的话）。在这种情况下，您应该使用一些servlet，当一个请求被发送到指定的URL时，将首先访问该servlet，并且在该servlet中，您使用a转发到所需的JSP，如

request.getRequestDispatcher（“/WEB-INF/JSP/index.JSP”）.forward（请求，响应）
HTTP ERROR 404

Problem accessing /home. Reason:

    Not Found
Powered by Jetty://

2013-10-08 20:27:31.652:WARN:oejs.ServletHandler:/home
java.lang.NullPointerException
    at java.net.URLEncoder.encode(URLEncoder.java:205)
    at java.net.URLEncoder.encode(URLEncoder.java:171)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:474)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:378)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:848)
    at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:669)
    at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:457)
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:137)
    at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:557)
    at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:231)
    at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1075)
    at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:384)
    at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:193)
    at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1009)
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:135)
    at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:255)
    at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:154)
    at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:116)
    at org.eclipse.jetty.server.Server.handle(Server.java:368)
    at org.eclipse.jetty.server.AbstractHttpConnection.handleRequest(AbstractHttpConnection.java:489)
    at org.eclipse.jetty.server.AbstractHttpConnection.headerComplete(AbstractHttpConnection.java:942)
    at org.eclipse.jetty.server.AbstractHttpConnection$RequestHandler.headerComplete(AbstractHttpConnection.java:1004)
    at org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:640)
    at org.eclipse.jetty.http.HttpParser.parseAvailable(HttpParser.java:235)
    at org.eclipse.jetty.server.AsyncHttpConnection.handle(AsyncHttpConnection.java:82)
    at org.eclipse.jetty.io.nio.SelectChannelEndPoint.handle(SelectChannelEndPoint.java:628)
    at org.eclipse.jetty.io.nio.SelectChannelEndPoint$1.run(SelectChannelEndPoint.java:52)
    at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:608)
    at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:543)
    at java.lang.Thread.run(Thread.java:724)

Oct 08, 2013 9:58:38 PM org.apache.jasper.servlet.JspServlet serviceJspFile
SEVERE: PWC6117: File "%2FUsers%2FuserName%2Fpersonal%2Friver%2Fsrc%2Fmain%2Fwebapp%2FWEB-INF%2Findex.jsp" not found